In a variable air volume, zoned, blow through unit with integrally packaged controls, a single variable speed fan supplies air for distribution to each of the zones. Each of the zones has a pair of independent dampers, a cooling damper and a neutral/heating damper, controlling the respective flow paths to the zone. The cooling damper is located in a first flow path downstream of the cooling coil which cools the air for all of the zones. The neutral/heating damper is located in a second flow path upstream of a selectively operated zone heating coil. The first and second flow paths combine downstream of the dampers which control the amount of flow to the respective zones. Due to the change in flow paths, either through the cooling damper or neutral/heating damper, and the unstable air flow from a zone plenum into a conventional flanged duct connection, establishing a stable zone air flow measurement point at the unit discharge is extremely difficult. One approach, often tried, to stabilize air flow is the use of a perforated metal plate. However, this causes a substantial increase in flow resistance with the resulting expenditure of additional fan energy. Further, the losses due to the resistance of the perforated plate cause problems for system powered devices which have been designed to close at pressures at least as low as 0.25 inches of water so that normally small losses become significant. Although velocity pressure can be determined as the difference between the total pressure and the static pressure at the throat of a venturi, only the throat is a proper measurement location so that different sensors would be required according to the sensed pressure range in order to remain within the range of highest sensor accuracy.